The present device relates to electrical engineering, especially to ignition devices for light composite fuels for internal combustion engines (ICE). It may be used with new ICE and with the old internal combustion engines that are already in operation.
Initiation of combustion of light composite fuels in the ICE is usually realised using a spark plug having an electric spark between the electrodes inserted into the combustion chamber formed at a given point in time due to high-voltage interelectrode sparkover.
Most spark plugs have the following components: housing, insulators and electrodes. The housing is usually equipped with screw thread for mounting the spark plug on the engine.
As a rule each ignition device accomplishes three tasks: the place, the method and the time of initiation of combustion. The time of initiation of combustion is not the subject of present invention.
Usually after fixing the spark plug in the engine the spark gap is located near the wall of the combustion chamber. The spark plugs of xe2x80x9copenxe2x80x9d design are widespread, where the spark gap is open to direct action of the fuel blend vortex. It is well known that the fuel blend vortex has a great speed especially near the combustion chamber wall. All this lead to two major drawbacks.
First, the ignition stability decreases. It is obvious at idling mode, at high gear it may cause ignition failure.
Second, the flame inside the combustion chamber spreads along the path of the said vortex. At first the flame spires to reach the central portion of the chamber, than it expands in a rather uniform way in all directions. The longer the spread path the higher is the sensitivity of the engine to the octane number. When accelerating the engine the torque prematurely decreases.
The fact of dissymmetry of combustion with respect to the centre causes a short-time thermodynamic unbalance of gas pressure on the piston bottom. The higher is the charge the stronger is the piston rotation around the point of support and it leads to short-term jams in the cylinder that causes the torque losses down to full stoppage of the internal combustion engine.
There are also the xe2x80x9cclosedxe2x80x9d design spark plugs where the spark gap is closed from direct action of the fuel blend vortex.
Those spark plugs have a flare effect that helps to overcome the said disadvantages of the xe2x80x9copenxe2x80x9d design spark plugs.
However those spark plugs have different efficiency. For example the spark plugs that conform to the specifications (USSR Inventors Certificate No. 1778842, cl. H01 T 13/00, 1981 and Japanese Patent No. 6-283250, cl. H01 T 13/20, 1994) cannot deliver a noticeable flame because of the small volume of fuel charge.
Other spark plugs, e.g. U.S. Pat. No. 3,842,819, cl. 123/169, 1974 and U.S. Pat. No. 3,892,991, cl. 313/138, 1976, are too xe2x80x9cclosedxe2x80x9d that worsen the fillability of the semi-isolated cavity with the fresh charge of fuel blend thus decreasing the ignition stability and the flame effect.
The Russian Federation Patent No. 2055432, cl. H01 T 13/54, 1996 describes the spark plugs having coaxial electrodes, where the spark is formed in a random location of the ring gap. Thus the flame becomes undesirably dissymetrical and its direction is random.
Now let us examine the method of burn initiation especially the nature of electric energy applied to the spark plug.
A classical ignition device uses a high-voltage ignition coil as a source of high-voltage electric energy. This coil stores the energy in the primary inductance. Such coils are rather bulky and heavy. They are known as xe2x80x9cheavy coilsxe2x80x9d.
The secondary high voltage is applied to the spark plug as a rule through a high-resistance circuit. After the high voltage sparkover of the spark gap the spark current is limited at a level of several dozens mA. Its duration is about 1 to 2 ms.
This rather slow method of application of electric energy decreases the ignition stability.
There is also a system where the ignition coil is mounted directly on the spark plug (German Patent No. 3915113). This design has some advantages. The coil is small because it does not store the energy; it is used as a high voltage pulse transformer. These coils are known as xe2x80x9clight coilsxe2x80x9d. Here the pulse duration may be shortened up to several microseconds and it is free from electric energy losses that occur in the high resistance connecting wires. This provides for high stability of ignition.
However this approach is very expensive to use in multicylinder internal combustion engine. Besides it is not enough reliable because the high voltage is badly compatible with high temperature in the coil.
The ignition device for internal combustion engine the most close to the present one is the device containing a spark plug with a housing where an electrical insulator, a central electrode and a housing electrode are placed, whereas the said electrodes form a spark gap and an electric energy storage device (U.S. Pat. No. 5,371,436).
This ignition device uses a capacitor as a capacitive storage that improves the ignition parameters.
The capacitor makes the ignition device independent from peculiarities of electric power source. Due to very low inductance and resistance of the capacitor and the spark plug the discharge of stored electric energy in the spark gap takes several dozens nanoseconds.
The increase of instantaneous power of the spark increases the ignition stability thus extending the mixture richness range. Besides, the electroerosion of spar plug electrodes.
This design has the following disadvantages:
during the short electric discharge a lot of energy is spent for radiation and formation of shock wave. Experiments have shown that the spark heat efficiency in case of capacitor discharge through low inductance does not exceed 20%.
the spark plug design does not allow the radiation energy and the shock wave to be of benefit for ignition because of dissipation inside the combustion chamber;
negligible flame effect.
The spark plug the most close the essence of present device is the spark plug including a housing, an insulator with a central electrode and a sidewall electrode attached to the housing and forming a spark gap between the said sidewall electrode and the end of the central electrode, where the space around the spark gap is covered with the internal conic surface of the housing expanding outwards (USSR Inventors Certificate No. 1720115).
This device has a disadvantage of absorption of a lot of thermal energy that reduces its efficiency.
The task of the present design of ignition device for internal combustion engine is to obtain the maximal flame effect and to increase the efficiency of internal combustion engine.
The technical result is obtained due to new ignition device for internal combustion engine containing a spark plug that includes a housing, an insulator with a central electrode and a sidewall electrode attached to the housing and forming a spark gap between the said sidewall electrode and the end of the central electrode, where the space around the spark gap is covered with the internal conic surface of the housing expanding outwards, and a capacitive electric energy storage device attached to the said spark plug, whereas the housing of the spark plug includes an attachment and a base part, where the attachment has an internal conic surface expanding outwards and a slot for sidewall electrode, where the attachment is made of a substance having low thermal conductance and low catalytic parameters.
The device is also characterised by the vertex angle of the conic surface of the attachment that makes 40 to 60xc2x0.